Question

Debye is a unit of:

• A. Dipole moment
• B. Field effect
• C. Dissociation constant
• D. Bond energy

Hint:

Dipole moment reflects the polarity of a molecule and is commonly expressed in Debye. Polar molecules like H\textsubscript{2}O have a higher dipole moment than nonpolar molecules like CO\textsubscript{2}.

Answer 1

The Correct Option is A

- The Debye (D) is a unit used to express the dipole moment of a molecule. Dipole moment is a measure of the separation of positive and negative charges in a molecule.
It is a vector quantity given by:
$$ \mu = q \times d $$ where \( \mu \) is the dipole moment, \( q \) is the magnitude of the charge, and \( d \) is the distance between the charges.
- 1 Debye (D) is equal to: $$ 1\ \text{D} = 3.336 \times 10^{-30}\ \text{Coulomb-meter} $$ - Dipole moments are important for understanding molecular polarity, solubility, and intermolecular interactions.
- Other options explained:
- (B) Field effect relates to electron withdrawal through space, not measured in Debye.
- (C) Dissociation constant is expressed in terms of concentration (mol/L).
- (D) Bond energy is measured in kcal/mol or kJ/mol.

Answer 2

The Debye is a specific physical unit, and the question is asking which physical quantity it measures. The way to answer this is to recall what each of the four listed quantities is normally measured in, and match that against what a Debye actually represents.

1. Dipole moment: Dipole moment measures the separation of positive and negative charge within a molecule and is defined as the product of the charge and the distance between the charges. Because this product works out to a very small number in SI units, chemists use the Debye as a convenient sized unit for it, with 1 Debye equal to about 3.336 times 10 to the power of negative 30 coulomb meters. This matches exactly what the Debye is used for.
2. Field effect: Field effect describes how a substituent influences a nearby group through space, mainly seen in acidity and reactivity trends. It is discussed qualitatively or through calculated electronic effects, not expressed in Debye units.
3. Dissociation constant: This quantity describes how much a compound splits into ions in solution and is expressed in concentration units such as moles per liter, not in Debye.
4. Bond energy: Bond energy measures the energy needed to break a chemical bond and is reported in units of energy such as kilojoules per mole or kilocalories per mole, which has nothing to do with the Debye scale.

Matching the definition of the Debye, a unit built from charge times distance, against each option shows it lines up only with dipole moment.

So the correct answer is Dipole moment.